1. Field
The embodiment(s) discussed herein is (are) related to a data communication device that is carried into or mounted on a vehicle to notify an external device of actual driving condition(s) in a road network, a data communication device for notifying an external device of driving condition(s) and receiving information about a time required to reach a destination from the external device, a data communication system, an information gathering method to be implemented in a traffic information providing system, and a recording medium storing a computer program for a data communication device.
2. Description of the Related Art
There have been services, such as telematics services, for providing the latest traffic information to drivers and passengers on vehicles. A service user may obtain information from a service center by using a terminal device such as a portable telephone device, a small-size computer, or a car navigation device, and connecting the vehicle to the Internet.
In this kind of services, automobiles driven by service users (hereinafter referred to as the user vehicles) are regarded as probe cars for information gathering. Accordingly, so-called vehicle information related to driving is transmitted as probe information from user vehicles to the service center. The service center processes the vehicle information from user vehicles actually driving on roads, so that the traffic information reflects the vehicle information. The service users not only receive information but also contribute to reinforcement and updating of the traffic information to be provided.
The traffic information to be provided contains the travel period of each link in a road network represented by nodes and links. A regular node is an intersection, and a link may be a section of a road divided by intersections. The travel period is the time required for a vehicle to pass through one link. The travel period is affected by traffic congestion and the weather, and normally varies among the time slots in each day. Based on the vehicle information from user vehicles, the service center determines the mean travel period of each link in each given time slot, and creates a database. In a car navigation system, for example, the travel periods provided from the service center are used for calculating the time required to travel from a departure point to a destination point. The required time is determined by adding up the travel periods of the respective links corresponding to the travel route from the departure point to the destination point.
Normally, the calculation of the travel period of each link is performed at the service center. Position measurement information indicating the current position is transmitted from each user vehicle to the service center at given intervals. (see Japanese Laid-Open Patent Publication Nos. 11-86184 and 7-129893)
A typical on-vehicle navigation device acquires position data (the latitude and longitude) at intervals of 0.1 to 1 second through a GPS reception device and a beacon reception device. The navigation device transmits the accumulated position data together with the respective acquired times to the service center at regular intervals of approximately 5 minutes. At the service center, a computer (hereinafter referred to as the server) provided in the center gathers the vehicle information from user vehicles, and accumulates the vehicle information in a memory.
Every 10 minutes or so, the server performs map matching about each user vehicle, and identifies the link the subject user vehicle has just passed through. The server then calculates the travel period of the identified link. If there is only the position data about part of the link, the travel period is hard to be determined. Therefore, the travel period calculation is put on hold till the next operation. The server performs processing on all the position data gathered over a given period of time, so as to count the number of passing vehicles and calculate the mean travel period for each link.
Other than the above system, there have been systems in which travel period calculations are performed on the vehicle side. Instead of a server, a navigation device mounted on a vehicle accumulates position data the navigation device has acquired over a given period of time. After performing map matching for determining a link at given intervals, the navigation device calculates the travel period of the link. The server at the service center gathers travel periods from vehicles, and updates the traffic information to be distributed to the vehicles. (see Japanese Laid-Open Patent Publication No. 2006-184084)